Puree Cherries: Place pitted cherries in a pot with a few tablespoons of water. Cook on low until juices release, then increase to medium heat and bring to a boil. Puree with a hand blender, then strain to remove skins. You should end up with about three-fourths of the original weight in puree.
1 pound cherries
Squeeze Lemon: Juice half a lemon.
1/2 lemon
Prep Eggs: Whisk together whole eggs, yolks, and sugar in a heatproof bowl.
2 eggs, 4 egg yolks, 3/8 cup white sugar
Cook Puree Mixture: Combine cherry puree and lemon juice in a pot; heat until it starts to bubble then remove from heat.
Temper Eggs: Gradually mix the hot puree into the egg mixture, a few tablespoons at a time, stirring constantly to prevent curdling.
Cook: Return all contents to the pot and cook on low, stirring continuously until the mixture thickens.
Add Butter: Off heat, stir in chopped butter until melted and incorporated.
4 oz butter
Taste Test: Adjust flavor with additional lemon juice or sugar as needed.
Strain (Optional): Strain the curd for a smoother texture, if desired.
Cover: Place plastic wrap directly on the surface to prevent skin formation.
Refrigerate: Allow to cool to room temperature, then refrigerate while still covered.